MAES IN THE AUTUMN OF 1877. 
247 
April number of the ‘ Monthly Notices,’ longitudes are measured 
from the first meridian eastwards, not westwards, as in Madler’s 
<diart, which in this respect I followed.) The northerly limit 
of this region is in lat. 45°. 
2. The region including J. Herschel Strait, Arago Strait, and 
Newton Strait, extending about 30° east and west of the first 
meridian, which passes through Dawes Forked Bay. 
3. De la Bue Ocean with Dawes Sea and Lockyer Sea, extend- 
ing as far east as Bessel Inlet. It extends between 240° and 
330° longitude, and reaches to 30° north lat. 
4. Hooke Sea and Maraldi Sea, with Huggins Inlet, Huy- 
ghens Sea and Bessel Inlet. Between 1 20° and 240° long, and 
reaching to 30° N. lat. 
5. Tycho and Delambre Seas, and the northern part of Dawes 
Strait (“ I have made a special study of this,” says Dr. Terby, 
as the least known of the Martial regions,” for which reason 
I have given all his questions relating to this region.) 
6. Beer, Airy, and Schroter Seas, Oudeman’s Inlet, and their 
relations with Bessel Inlet and Huggins Inlet. 
The two last regions complete the surface of the planet, 
extending from 30° north latitude to the northern pole. 
Great interest will attach to the study of such changes as 
may be produced by the formation and dissipation of clouds 
over the surface of Mars, or the melting of snows either with 
the progress of the Martian year or possibly even during the 
course of the Martian day. The approaching opposition occurs 
about a fortnight before Martian midsummer for the southern 
hemisphere, the date of which is about September 1 8. As the 
melting of the snows which surround the southern hemisphere 
will probably reduce that snow-cap to a minimum about a month 
later, observers will have a very favourable opportunity of study- 
ing the reduction of the southern snows. Moreover, the small- 
ness of the snow-cap will render it easier to ascertain whether 
its centre is coincident with the south pole, or, as is now 
generally believed, measurably displaced from that point. 
Observations directed to this end cannot but be regarded as 
extremely interesting. They will not only help to determine 
the true position of the Martian pole, but also to indicate 
the position of some of the midsummer isotherms for the 
southern hemisphere. According to the observations heretofore 
made, it would appear that the southern snow-cap reaches 
furthest from the pole in about longitude 30° east of the first 
meridian. 
A few words may be added here respecting the nomenclature 
in my map. When I was constructing my chart of Mars, I 
proposed to write a treatise upon the planet. That was in 
